In conventional roller grill assemblies, an array of roller tubes are rotatably mounted within a housing. Each roller tube may be heated, providing that the heat is then transferred to food placed on the roller tubes.
One drawback of a conventional roller grill assembly is the temperature variance along the length of the roller tubes. A single, homogeneous heating element running along the length of a roller tube generally results in hotter tube surfaces at the middle of the roller tube than at the distal, or outer, ends of the roller tube. Thus, food positioned toward the outer ends of the roller tubes are not heated to the same temperature as food positioned near the middle of the roller tubes. The differences in heating temperatures results in uneven cooking of the food products. Other devices attempt to address this issue by utilizing variable heating elements, or even multiple heating elements. These devices allow for controlled variations of the heating element wattage along the length of the roller tubes. However, these designs also increase the complexity of the device, and thereby increasing the cost, and fail to entirely solve the problem.
Surfaces of the roller tube, near the ends of the tubes provide the most convenient location to mount one or more temperature probes. This configuration results in measurement of a temperature that is inherently offset, or skewed, from the actual temperature of the food products. The temperature skew, or offset, is a direct result of the delay when measuring heat transferred from the food, then to the roller tube surfaces, and finally to the temperature probe through the surface and mounting bracket for the temperature probe. Therefore, the measured temperature is time-delayed based on the time required for the various parts of the system to reach a temperature equilibrium, which rarely happens. As a result, the correlation between the food temperature and the probe-measured temperature is adversely impacted.
The potential to undercook or overcook food due to the wide temperature variations along both the length of the roller tube and over time. The aforementioned delay in translating the temperature variations quickly to the temperature probe makes it difficult to precisely control the heating elements. Therefore, heating elements are frequently turned on too late, or may stay on for too long of a period to maintain a consistent temperature. Therefore, conventional methods of measurement and control are unable to respond accurately and quickly to these temperature variations.
Some conventional roller grill assemblies provide a control that cooks food products initially, while then switching to a hold mode to maintain product temperature at a safe level. The holding temperature is set lower than the cooking temperature to prevent the food products from overcooking, while also maintaining a safe temperature for holding the food. This holding temperature ensures that the quality and safety of the food products over an extended period of time. However, when a conventional roller grill assembly switches from a cook mode to a hold mode, the food products on the roller tubes tend to drop in temperature faster than the measurement probe can detect due to the exposure of the food products to the ambient air and the aforementioned equilibrium delay. This results in food products that may drop below a safe holding temperature for a period of time before the holding mode raises the temperature of the food products above that threshold.
A conventional roller grill assembly may also provide a warming area for related food products, such as a bun warmer for hot dogs. However, the heating of both a series of roller tubes and a warming area can result in a substantially higher current draw than a roller grill assembly without a warming area. This higher current draw requires an end user to provide a larger electrical circuit for powering the roller grill assembly, which can significantly increase the cost of installing such a system and is inefficient since the peak current draw tends to be much higher than the average draw.
Furthermore, roller tubes of a conventional roller grill assembly are generally provided with a smooth finish. However, after the fatty oils of a food product are released during the cooking process, the oils have a tendency to adhere to the outer surfaces of the roller tube. These oils decrease the friction between the roller tube and the food products, which results in food products fail to rotate due to the undesirable slipping of the product on the tubes. Food products that are not evenly turned may cook unevenly and, in certain circumstances, may fail to even reach a safe temperature.
In view of the foregoing, there exists a need for a roller grill assembly that provides more accurate and responsive heating temperature control than the prior art systems. There also exists a need for a roller grill assembly that provides even and effective heating along the entire length of the roller tubes. Additionally, there exists a need for a method of limiting current draw in different heating areas of a roller grill assembly, such as a cooking area and a warming area, enabling the use of smaller electrical circuits for operation. Furthermore, there exists yet another need to provide improved surfaces for roller tubes in a roller grill assembly, to prevent undesirable sliding or slipping of the food products. The present invention addresses these needs.